Tank clock



FIG. 1 is a front perspective view of a tank clock showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a back elevational view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a right side view thereof; and,

FIG. 7 is a left side view thereof. 

The ornamental design for a tank clock, as shown. 